This invention relates to the field of water treatment and, more particularly, to an apparatus for feeding substantially uniform amounts of a chemical into a liquid stream having an irregular flow pattern.
In the treatment of waste water there is a need for a reliable chemical feeding device that can feed substantially uniform amounts of a chemical to waste water which typically flows at an irregular rate. In many homes sewage is treated in an anaerobic septic system. The sewage enters a large tank where the solid and organic matter is decomposed by anaerobic bacteria present in the sewage. Water from the septic tank is skimmed off and generally goes into a tiled field, where the water is absorbed into the ground. The filtration which naturally occurs by the seepage of the water through the ground is in some cases sufficient to purify the water as it returns to the fresh water table. This scheme is satisfactory if the population of septic systems is kept low and there is a reasonable amount of sandy soil through which the discharged water can percolate. However, in many instances the soil is too rocky for proper filtration to occur. This results in biologically contaminated water rising to the surface or getting into the fresh water supply. In addition to considerations of bacterial contamination, instances of chemical ions, such as phosphate and nitrate ions, entering rivers and streams is becoming a significant disturbing factor in the ecological balance.
Various systems have been proposed for feeding appropriate chemicals, such as hypochlorous acid, into the effluent of the septic tank. However, the irregular flow of waste water gives rise to serious problems of regulating the concentration of chemicals added to waste water. For example, if the rate of addition of chemicals were constant, then the resulting concentration would be too low during peak periods and too high during low periods of waste water flow. Accordingly, existing systems often include complex and expensive pumps, sensing systems, and/or regulating valves which attempt to adjust the flow rate of waste water or the feed rate of chemicals. In addition to being expensive, the complexity of these systems renders them unreliable.
It is an object of this invention to provide a reliable and relatively inexpensive apparatus which is responsive to the prior art problems as set forth.